1. Field of the Invention
The invention relates to a method of processing circulated water, in particular bath water and water in air treatment plants, the water being treated with ozone, filtered and mixed with a flocculant and an ozone-reducing halogen, in particular bromine and/or iodine.
2. Background of the Art
A known method of this type is shown diagrammatically as Example 4 on page 64 in the company publication "Wasser-Aufbereitung mit dem Ozon-Oxidator" ("Water Processing with the Ozone Oxidizer") of Hydro-Elektrik GmbH, Angelestra.beta.e 50, D-7980 Ravensburg 19, from 1985. The flocculant is introduced into the water in the flow direction upstream of the sand filter by means of a metering pump in regular bursts or continuously. In the automatic mode, the metering pump is switched on for as long as the water circulating pump is running. In the filter, the entire flocculant introduced is retained, together with the corpuscular particles bound by its action. Then the water is treated with ozone in the reaction vessel of a treatment plant and then flows back into the pool. Hydrogen bromide is added once to the water as halogen when the pool is first filled. The chosen bromine content then remains practically constant. Only when a part of the water has been supplemented by fresh water, for example the part used for back-flushing the filter, is the hydrogen bromide topped up accordingly.
A disadvantage is that the chemical auxiliary processing agents are introduced into the water regardless of the actual requirement. Specifically, whereas the pollution of the water changes continuously, for example as a result of the organic substances of every kind introduced irregularly by new bathers arriving, the metering of the auxiliary processing agents remains constant. The set values correspond to the maximum pollution to be expected and are therefore too high in normal operation. For example, flocculant added in excess results in an increase in the filter resistance or even in filter blockage and necessitates premature filter back-flushing. However, this requires an unnecessary consumption of fresh water and pollutes the waste water system.
The bromide present in the water is known to react with ozone according to the equation EQU O.sub.3 +Br.sup.- =O.sub.2 +BrO.sup.-.
In this process, hypobromite (BrO.sup.-) and presumably also higher-valency unstable bromine oxides such as, for example, BrO.sub.2 and BrO.sub.3, which act as disinfectants and are accompanied by high redox potentials are produced. However, it has been found that both too high and too low redox potentials are disadvantageous.
The object of the invention is to propose a method which rapidly degrades the organic pollution and guarantees an always perfect chemico-physical and hygienic quality of the circulated water with minimum addition of auxiliary processing agents. In addition, the method to be proposed should not only fulfil the applicable standards and regulations relating to the water quality, but should at the same time take into consideration tightened standards and environmental regulations to be expected. These include, in particular, the reduction of the concentration of trihalomethanes (THM) in the bath water to values below 0.01 mg/l.